Department of Biology, Boston University, Boston, Massachusetts, USA.
Department of Integrative Biology, University of Texas at Austin, Austin, Texas, USA.
Mol Ecol. 2024 Apr;33(8):e17318. doi: 10.1111/mec.17318. Epub 2024 Mar 15.
Increasing ocean temperatures are causing dysbiosis between coral hosts and their symbionts. Previous work suggests that coral host gene expression responds more strongly to environmental stress compared to their intracellular symbionts; however, the causes and consequences of this phenomenon remain untested. We hypothesized that symbionts are less responsive because hosts modulate symbiont environments to buffer stress. To test this hypothesis, we leveraged the facultative symbiosis between the scleractinian coral Oculina arbuscula and its symbiont Breviolum psygmophilum to characterize gene expression responses of both symbiotic partners in and ex hospite under thermal challenges. To characterize host and in hospite symbiont responses, symbiotic and aposymbiotic O. arbuscula were exposed to three treatments: (1) control (18°C), (2) heat (32°C), and (3) cold (6°C). This experiment was replicated with B. psygmophilum cultured from O. arbuscula to characterize ex hospite symbiont responses. Both thermal challenges elicited classic environmental stress responses (ESRs) in O. arbuscula regardless of symbiotic state, with hosts responding more strongly to cold challenge. Hosts also exhibited stronger responses than in hospite symbionts. In and ex hospite B. psygmophilum both down-regulated gene ontology pathways associated with photosynthesis under thermal challenge; however, ex hospite symbionts exhibited greater gene expression plasticity and differential expression of genes associated with ESRs. Taken together, these findings suggest that O. arbuscula hosts may buffer environments of B. psygmophilum symbionts; however, we outline the future work needed to confirm this hypothesis.
海洋温度升高正在导致珊瑚宿主与其共生体之间的失调。先前的工作表明，与细胞内共生体相比，珊瑚宿主的基因表达对环境胁迫的响应更为强烈；然而，这一现象的原因和后果仍未得到检验。我们假设共生体的响应较弱，是因为宿主调节共生体的环境来缓冲胁迫。为了检验这一假设，我们利用硬珊瑚 Oculina arbuscula 与其共生菌 Breviolum psygmophilum 之间的兼性共生关系，在热胁迫下，从宿主内外两个方面来描述共生伙伴的基因表达响应。为了描述宿主和体内共生体的响应，将共生和非共生的 O. arbuscula 暴露于三种处理中：（1）对照（18°C），（2）热（32°C），和（3）冷（6°C）。该实验用从 O. arbuscula 中培养的 B. psygmophilum 进行了重复，以描述体外共生体的响应。这两种热胁迫都在无论共生状态如何的情况下，引发了 O. arbuscula 的经典环境胁迫反应（ESR），而宿主对冷胁迫的响应更为强烈。宿主的反应也比体内共生体更强。在体内和体外的 B. psygmophilum 中，热胁迫下都下调了与光合作用相关的基因本体论途径；然而，体外共生体表现出更大的基因表达可塑性和与 ESR 相关基因的差异表达。综上所述，这些发现表明，O. arbuscula 宿主可能缓冲 B. psygmophilum 共生体的环境；然而，我们概述了未来需要开展的工作，以证实这一假设。
